This invention is directed to optical scanning devices, such as bar code scanners, and is more particularly concerned with an arrangement for reading optical symbols, e.g., small linear or two-dimensional bar code symbols that are directly marked on articles. The invention is more particularly concerned with a combination of a hand-held optical scanner and a black-light illuminator that provides stimulating illumination onto a bar code symbol or other symbol which is formed of a phosphorescent or luminescent material.
Within the past several years, two-dimensional bar code systems have begun to be employed on small articles so that the article can be tracked throughout manufacturing, packaging, and shipping. In some cases, luminescent or fluorescent bar code symbols are invisibly printed onto articles, e.g., onto the base or bottom of a pharmaceutical vial to identify the contents, as well as to provide information about the batch number, date and place of manufacture. Where 2-D symbols are used, these can carry all the required information within a square that may typically be only three millimeters on a side. The symbols can be screen printed or ink-jet printed directly onto the surface or the pharmaceutical vial or other article. At present, machine-mounted camera-based scanner systems are employed, in which the articles proceed past the scanner station, and the articles receive illumination from a discharge-tube type black light source. These scanner systems are bulky and non-portable, so they cannot be carried by an operator. This makes it impossible to read the bar codes in a warehouse, shipping dock or receiving dock environment where the workers could be provided with hand-held scanners. In addition, because of the rather harmful effects from ultraviolet radiation, conventional black light sources typically have to be shielded to protect the workers from exposure to skin or eyes. Consequently, invisibly printed phosphorescent bar code symbols can only be read under special circumstances, as the bulk, weight, and complexity of the reader equipment has limited their widespread usage.
Only recently have short-wavelength diodes, i.e., LEDs, been introduced. There are now LEDs that can emit light in the deep blue to near UV region of the spectrum, and can be used to produce black-light illumination. These have been used notably, in combination with an encapsulation of luminescent phosphors, to create so-called white LEDs, in which the short-wavelength light stimulates the phosphors to create a blend of red, green, and blue light. No one has considered using black-light emitting diodes in connection with any sort of hand-held scanner device to permit their use in reading xe2x80x9cinvisiblexe2x80x9d luminescent or fluorescent optical symbols, such as bar codes.
Accordingly, it is an object of this invention to provide an improved hand-held optical symbol scanner that avoids the drawbacks of the prior art.
It is another object to provide a hand-held scanner that is safe and convenient to use for reading invisibly printed fluorescent optical symbols.
It is a further object to provide a hand-held scanner and illuminator that permits a user to read and accurately decode a fluorescent or phosphorescent symbol that has been directly printed on an article and which scanner employs one or more low-power far-blue, UV/blue, UV or similar black-light source, contained within an illuminator portion of the hand-held scanner.
It is still a further object to provide a black-light illuminator that fits on or mounts onto the distal or front of an available hand-held 2-D bar code scanner, so that the scanner can be used in a variety of factory, warehouse, shipping, or retail (e.g., pharmacy) environments.
It is a more specific object that the black-light illuminator be incorporated into the working or distal face of the scanner so that the scanner will pick up the invisible bar code symbol as a pattern of bright and dark regions.
According to one aspect of this invention, a scanner assembly is configured for detecting and decoding a small scale two dimensional optical symbol, such as a 2-D bar code symbol, lying on a surface of an article. The scanner assembly can be a portable (hand-held) contact device, and can be easily adapted for wireless battery-powered operation.
The optical symbol scanner assembly here is adapted for detecting and decoding any of a variety of a bar code symbols or other visible symbol that lies on the surface of an article, with the symbol comprising a pattern of luminescent and non-luminescent areas that can identify lot number and origin of an item. This scanner assembly can be used to advantage in the pharmaceutical, automotive, and other industries, in connection with pharmaceutical vials, security-marked items, consumer product sub-assemblies, and many other types of items. The optical symbol scanner assembly is adapted for detecting and decoding a phosphorescent or luminescent symbol, i.e., a pattern of fluorescent markings non-fluorescent surface, in which the fluorescent markings glow or fluoresce in the presence of black light radiation.
The hand-held scanner device has a housing, with a distal face and light-generating means on the distal face of the housing. This light-generating means produces the black-light illumination and directs it to fall on the luminescent or phosphorescent symbol. The light generating means includes at least one black-light emitting diode, and preferably an array of such diodes. A focusing lens group is positioned on the optic axis of the scanner for focusing an image of the symbol onto a solid-state imager device positioned proximally of the lens group within the scanner device. In a preferred embodiment, an array of LEDs is mounted at the distal face of the scanner housing and the LEDs are spaced left and right of the optic axis.
A nosepiece, i.e., a shield or shroud, is mounted on the distal face of the scanner device, and has an optical passageway whose optic axis is aligned with the optic axis of the scanning device. An illumination channel within the shield conducts the illumination, that is, directs and guides the black light emitted by the diodes, so that black light illumination impinges on the symbol and the scanner device views an image of the symbol as produced by its fluorescent markings.
Preferably, the nosepiece is in the form of a hollow shroud, and includes at a distal end thereof a dust window of a material that is transparent to black light illumination. The window can be a transparent plate that is tilted, i.e., oriented at a non-right angle, with respect to the optic axis.
The nosepiece or shield can be formed acrylic material or equivalent, and provided with an opaque coating.
The black-light producing LEDs are preferably of the type that produce illumination in the far blue to near ultraviolet region, i.e., between 350 run and 420 run, and preferably between about 390 nm and 405 nm.
An optical filter is interposed along the scanner""s optical axis in advance of the imager device. This may be a yellow or orange filter for passing light that fluoresces from the markings, but blocking the black light from the diodes so that the illumination does not flood and blind the imager.
In the preferred embodiments of this invention, the bar code symbols emit visible, i.e., white light when stimulated by the far blue or UV radiation, and the imager device in the scanner is configured to respond to visible light images. However, the invention is not limited only to these embodiments, and it is possible for scanners of this invention to be employed with bar code symbols that emit other wavelengths when illuminated with black light.
Available diodes can have a principal wavelength of 370, 390, or 405 nm, e.g., and 405 nm is preferred as it does emit an amount of blue light that is sufficiently visible to indicate when the device is ON. These devices all emit what is generally referred to as black light illumination, that is, wavelengths sufficiently short (energetic) so as to stimulate the fluorescent materials used in printing the bar coded symbols to produce visible light that can be picked up by the imager in the scanner. The stimulating light can be in the blue (or violet) end of the visible spectrum or beyond it in the UV region.
In order to accommodate these black-light diodes, the power circuitry within the scanner has to be modified slightly. While the usual red and IR LEDs that are conventionally used have a forward voltage of about 1.8 volts, the blue and UV LEDs used in embodiments this invention require a forward voltage of about 3.7 volts. This means that where the conventional scanner has its red or IR LEDs connected in series, the scanner with the black light diodes will have to place the diodes in parallel, with a further series dropping resistance so that the illuminator can operate in the same environment and produce the required black light illumination.
The nosepiece is preferably in the shape of a truncated pyramid, i.e., frustum of a pyramid, and may be formed conveniently of acrylic sheet, and coated or covered with a black (opaque) coating material. Other opaque materials may be used. A suitable warning label placed on a top surface of the nosepiece warns the user against potential injury from the radiation.
The above and many other objects, features, and advantages of this invention will present themselves to persons skilled in this art from the ensuing description of preferred embodiments of this invention, as described with reference to the accompanying Drawing.